1. Related Applications
There are no applications related hereto heretofore filed in this or any foreign country.
2. Field of Invention
My invention relates generally to the classifying and separating of magnetically susceptible particles from a diamagnetic particulate mass and more particularly to a machine that uses a plurality of eccentrically rotating cylinders so to do in a batch type process.
3. Description of Prior Art
The physical separation of ferromagnetic and paramagnetic particles from a diamagnetic particulate mass by use of magnetic forces has been long known and has been employed in the beneficiation of ores especially in dealing with materials of at least medial magnetic susceptibility. The instant invention provides a new and novel machine to apply such magnetic separating principles in a particular fashion, especially to beneficiate particulate ores carrying the platinum group of metals.
Magnetic separators, especially as used in ore processing, have been the subject of recent advancements which have made them quite sophisticated. In general, however, these known mechanisms have dealt largely with ferromagnetic materials that have strong magnetic susceptibility and are relatively inexpensive per unit of mass and therefore have been designed to deal with massive quantities of material by automated mechanisms that generally do not have finely controllable operating parameters. Most magnetic separators of present day commerce fall broadly into three distinguishable classes:
In a first class the material to be treated is spread in a thin layer on a horizontal belt and the more highly magnetically susceptible material is attracted away from the less magnetically susceptible material against the force of gravity to be thereafter carried away from the magnetic field for recovery. In a separator known as the Rowand-Wetherill mechanism, the magnetically susceptible material is carried away by a belt running at right angles to the travel of the feed belt. In another version of mechanism using this same principle the belt removing magnetically susceptible material runs in the same direction as the feed belt, parallel to it and under a series of magnets so that the magnetically susceptible material is carried along until it is outside of the field of the lower magnets and then dropped.
A second type of magnetic separator provides a horizontal feed belt passing around a magnetic pulley so that non-magnetic material will be dropped at the end of the belt whereas magnetically susceptible material will cling to the belt as it passes around the pulley and be dropped rearwardly of the pulley when that material leaves the magnetic field so that it can be there physically separated. This is the principle of the so-called Dings magnetic pulley which is used especially for the removal of tramp iron. Variations of this device may provide more sophisticated separations of particulate matter having various magnetic permeabilities by using a non-magnetic pulley, such as of brass, and placing fixed magnets in different circumferential locations so that the magnetically distinguishable material drops at specifically designated points and may there be separated.
A third common type of magnetic separator induces a highly concentrated magnetic force in a roller over which a horizontal belt carrying particulate matter passes so that the material falling in a downstream over it will have varying positioning depending upon the magnetic permeability. One or more lips may be inserted in the down falling particulate stream to separate material of different magnetic permeability. This same principle is applied in some mechanisms by placing a strong magnetic source laterally adjacent the downwardly falling stream of material so that magnetic permeable particles will be moved in a horizontal plane by the magnetic force and may be separated therebelow by reason of position.
All of these separators are of a continuous process type and generally do not provide any fine degree of either control or separation. Though these separators have been used for paramagnetic material other than ferromagnetic, and especially the platinum group of metals, they have not been particularly effective for this purpose, largely because of their lack of sophisticated control and the peculiar nature of the platinum group of metals-comprising platinum, iridium, osmium, ruthenium, rhodium and palladium. All of these metals are actually paramagnetic though rhodium and iridium are so low in their paramagnetism that they sometimes have been classified, even by authoritative sources, as diamagnetics. These particular metals are invariably intermixed in their occurrence and generally are difficult of chemical separation and nearly impossible of physical separation. The members of this group of metals inter-form solid solutions and various alloys, many of which may be intermixed either physically or possibly chemically. Depending somewhat upon crystal state it appears that each metal may under proper conditions be miscible in the other and most alloys do not have constant compositions. Commonly crystals of varying alloys may occur simultaneously in an intergrown fashion in a single material and it is commonplace to find minute grains of one alloy, measuring in the micron range, present in another. The magnetic properties of various chemical or physical mixtures of the platinum group metals are not necessarily predictable from the magnetic properties of their progenitors and in fact may differ widely therefrom. Nonetheless magnetic separation of various platinum metal compositions from ores remains one of the simplest and most effective methods of beneficiating these ores. The instant invention seeks to provide a mechanism to more effectively accomplish magnetic separation and recovery of both the platinum metals and other paramagnetics than could be accomplished by prior art devices.
I provide a batch type magnetic separator rather than a continuously operating mechanism to allow better control of time of magnetic separation and to allow longer elapsed periods for processing than may generally be had with the continuous dynamic systems.
Since the magnetic force exerted by a particular magnetic source varies as the square of the distance from that source it is important that magnetically susceptible materials to be separated are brought into contact or close association with the magnetic source. In this regard it should be remembered that the magnetic permeability through gangue between a magnetic source and magnetic particles may be substantially different, normally less, than the permeability through an air gap of the same distance. This is a substantial problem with the continuous dynamic processes of magnetic separation since it is generally difficult to maintain a thin stream of material in uniformly close adjacency to a magnetic source and because of this the efficiency of separation may be quite low. My invention solves this problem by providing a plurality of relatively small, magnetic cylinders rotating eccentrically in a horizontal bed of particulate material. Both the rotation of the surface of the magnetic cylinders and their eccentricity cause them to move adjacent particulate matter and to move their physical position relative to the particulate matter, both of which motions tend to increase the probability that an average particle will be brought much closer to a magnetic source than with the other dynamic separators. This action is especially beneficial in dealing with fine particles in the micron size range.
My invention also provides aluminum cylinders about the peripheral surface of its magnetic sources. It has been found empirically that this type of magnetic source is more efficient in magnetically separating the platinum group of metals and their mixture than other types of magnetic sources. The reason for this phenomenon is not definitely known but apparently the aluminum case about the magnetic cylinders act somewhat as a magnetic catalyst, similarly in the physical arena to the action of an ordinary catalyst in a chemical reaction. For whatever reason, it has been found that separation of platinum metals from their ores is substantially more efficient when magnetic cylinders having an aluminum periphery are used than when magnetic cylinders having a ferromagnetic surface are used.
My invention thusly differs from the prior art either individually or in combination in providing a new, novel and unique batch type magnetic separator.